Cortical inhibition and excitation in abstinent cocaine-dependent patients: a transcranial magnetic stimulation study

Neuroreport. 2007 Feb 12;18(3):289-92. doi: 10.1097/WNR.0b013e3280143cf0.


Prior transcranial magnetic stimulation studies showed that resting motor threshold is elevated in abstinent cocaine-dependent patients, suggesting a decrease in axonal excitability. In contrast, the increased incidence of seizures and psychosis in this group suggests increased excitability or decreased inhibition. Here, we studied long-interval intracortical facilitation and long-interval intracortical inhibition, paired-pulse transcranial magnetic stimulation measures that are more directly linked to glutamatergic cortical facilitation and GABAergic inhibition, respectively. Ten cocaine-dependent and 10 healthy controls were examined. Resting motor threshold, long-interval intracortical facilitation and long-interval intracortical inhibition were tested from the left motor cortex. The cocaine group showed an elevated resting motor threshold and an increased long-interval intracortical facilitation, whereas long-interval intracortical inhibition was normal. Although the increase in long-interval intracortical facilitation suggests exaggerated cortical glutamatergic excitability, the increase in resting motor threshold may signify a protective mechanism against seizures and psychosis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Brain / drug effects
  • Brain / physiopathology*
  • Cocaine / adverse effects*
  • Cocaine-Related Disorders / diagnosis
  • Cocaine-Related Disorders / physiopathology*
  • Dopamine Uptake Inhibitors / adverse effects
  • Evoked Potentials, Motor / physiology
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • Female
  • Glutamic Acid / metabolism
  • Humans
  • Male
  • Middle Aged
  • Motor Cortex / drug effects
  • Motor Cortex / physiopathology
  • Neural Inhibition* / drug effects
  • Neural Inhibition* / physiology
  • Substance Withdrawal Syndrome / diagnosis
  • Substance Withdrawal Syndrome / physiopathology*
  • Synaptic Transmission* / drug effects
  • Synaptic Transmission* / physiology
  • Transcranial Magnetic Stimulation
  • gamma-Aminobutyric Acid / metabolism


  • Dopamine Uptake Inhibitors
  • Glutamic Acid
  • gamma-Aminobutyric Acid
  • Cocaine